Backup of Virtual Machines Using Cloned Virtual Machines

1. A method for creating a backup of a first virtual machine running on a first host computer in a network of host computers, comprising: generating a second virtual machine running on a second host computer in the network of host computers, the second virtual machine being a copy of the first virtual machine, said generating comprising: generating the second virtual machine in a suspended state on the second host computer; transferring a copy of memory and non-memory state information associated with the first virtual machine to the second virtual machine, said transferring comprising; while the first virtual machine is running, transferring a complete copy of the memory state information to the second virtual machine, and iteratively identifying items of the memory state information that were modified after copies of the items were transferred to the second virtual machine and retransferring copies of the identified items to the second virtual machine until the number of identified items falls below a predetermined threshold; placing the first virtual machine in a suspended state; while the first virtual machine is in the suspended state, transferring a copy of the non-memory state information to the second virtual machine; and retransferring to the second virtual machine copies of any remaining identified items of memory state information that were modified after copies of the items were transferred to the second virtual machine; and placing the first virtual machine back in a running state; creating a virtual disk for the second virtual machine, said creating the virtual disk for the second virtual machine comprising obtaining a copy of a virtual disk associated with the first virtual machine; and placing the second virtual machine in a running state; obtaining a snapshot of the virtual disk associated with the second virtual machine; and creating a first backup based on at least the snapshot of the virtual disk associated with the second virtual machine.

2. The method of claim 1 , wherein obtaining the snapshot of the virtual disk associated with the second virtual machine comprises: initiating an orderly shutdown of the second virtual machine; and obtaining the snapshot of the virtual disk associated with the second virtual machine after the orderly shutdown of the second virtual machine is complete.

3. The method of claim 1 , wherein obtaining the snapshot of the virtual disk associated with the second virtual machine comprises: temporarily quiescing at least one application executing on the second virtual machine; and obtaining the snapshot of the virtual disk associated with the second virtual machine while the at least one application is in the quiesced state.

4. The method of claim 1 , wherein obtaining a copy of a virtual disk associated with the first virtual machine comprises obtaining a writeable snapshot of the virtual disk associated with the first virtual machine.

5. The method of claim 1 , wherein generating the second virtual machine running on the second host computer further comprises: disabling one or more connections between the second virtual machine and one or more external entities.

6. The method of claim 5 , wherein generating the second virtual machine running on the second host computer further comprises: establishing a private connection to the second virtual machine; and using the private connection to trigger an orderly shutdown of the second virtual machine prior to the obtaining of the snapshot of the virtual disk associated with the second virtual machine.

7. The method of claim 1 , further comprising: generating a third virtual machine running on a host computer in the network of host computers, the third virtual machine being a copy of the first virtual machine at a point in time after the a virtual disk associated with the first virtual machine was copied to create the virtual disk associated with the second virtual machine; obtaining a snapshot of a virtual disk associated with the third virtual machine; and creating a second backup based on at least the snapshot of the virtual disk associated with the third virtual machine.

8. The method of claim 7 , wherein creating the second backup based on at least the snapshot of the virtual disk associated with the third virtual machine comprises creating an incremental backup, wherein creating the incremental backup comprises: tracking changes to the virtual disk associated with the first virtual machine between a point in time at which the virtual disk associated with the first virtual machine was copied to create the virtual disk associated with the second virtual machine and a point in time at which the virtual disk associated with the first virtual machine was copied to create the virtual disk associated with the third virtual machine; tracking changes to the virtual disk associated with the second virtual machine; and tracking changes to the virtual disk associated with the third virtual machine.

9. A system, comprising: a first host computer comprising a first virtualization layer, a first virtual machine executing on the first virtualization layer, first cloning logic within the first virtualization layer, and first backup logic; a second host computer connected to the first host computer, the second host computer comprising a second virtualization layer, second cloning logic within the second virtualization layer, and second backup logic; the first and second cloning logic being configured to generate a second virtual machine on the second host computer responsive to the initiation of a backup process by the first and/or second backup logic, the second virtual machine being a copy of the first virtual machine, the first and second cloning logic being configured to generate the second virtual machine running on the second host computer by: generating the second virtual machine in a suspended state on the second host computer; transferring a copy of memory and non-memory state information associated with the first virtual machine to the second virtual machine, the first and second cloning logic being configured to transfer the copy of the memory and non-memory state information associated with the first virtual machine to the second virtual machine by: while the first virtual machine is running, transferring a complete copy of the memory state information to the second virtual machine; and iteratively identifying items of the memory state information that were modified after copies of the items were transferred to the second virtual machine and retransferring copies of the identified items to the second virtual machine until the number of identified items falls below a predetermined threshold; placing the first virtual machine in a suspended state; while the first virtual machine is in the suspended state, transferring a copy of the non-memory state information to the second virtual machine; and retransferring to the second virtual machine copies of any remaining identified items of memory state information that were modified after copies of the items were transferred to the second virtual machine; and placing the first virtual machine back in a running state; creating a virtual disk for the second virtual machine, said creating the virtual disk for the second virtual machine comprising obtaining a copy of a virtual disk associated with the first virtual machine; and placing the second virtual machine in a running state; the second backup logic being configured to obtain a snapshot of the virtual disk associated with the second virtual machine and to create a first backup based on at least the snapshot of the virtual disk associated with the second virtual machine.

10. The system of claim 9 , wherein the second backup logic is configured to initiate an orderly shutdown of the second virtual machine and obtain the snapshot of the virtual disk associated with the second virtual machine after the orderly shutdown of the second virtual machine is complete.

11. The system of claim 9 , wherein the second backup logic is configured to temporarily quiesce at least one application executing on the second virtual machine and obtain the snapshot of the virtual disk associated with the second virtual machine while the at least one application is in the quiesced state.

12. The system of claim 9 , wherein the first and second cloning logic is configured to obtain a copy of the virtual disk associated with the first virtual machine by obtaining a writeable snapshot of the virtual disk associated with the first virtual machine.

13. The system of claim 9 , wherein the first and second cloning logic is configured to generate the second virtual machine running on the second host computer by disabling one or more connections between the second virtual machine and one or more external entities.

14. The system of claim 13 , wherein the first and second cloning logic is further configured to generate the second virtual machine running on the second host computer by establishing a private connection to the second virtual machine and using the private connection to trigger an orderly shutdown of the second virtual machine prior to the obtaining of the snapshot of the virtual disk associated with the second virtual machine.

15. A method for creating a backup of a first virtual machine running on a first host computer in a network of host computers, comprising: generating a second virtual machine running on a second host computer in the network of host computers, the second virtual machine being a copy of the first virtual machine; obtaining a snapshot of a virtual disk associated with the second virtual machine; generating a third virtual machine running on the second host computer, the third virtual machine being a copy of the first virtual machine; obtaining a snapshot of a virtual disk associated with the third virtual machine; and creating an incremental backup based on at least the snapshot of the virtual disk associated with the second virtual machine and the snapshot of the virtual disk associated with the third virtual machine.

16. The method of claim 15 , wherein creating the incremental backup comprises: tracking changes to a virtual disk associated with the first host computer between a point in time at which the virtual disk associated with the first host computer was copied to create the virtual disk associated with the second virtual machine and a point in time at which the virtual disk associated with the first host computer was copied to create the virtual disk associated with the third virtual machine; tracking changes to the virtual disk associated with the second virtual machine between a point in time at which the virtual disk associated with the second virtual machine was created and a point in time at which the snapshot of the virtual disk associated with the second virtual machine was obtained; and tracking changes to the virtual disk associated with the third virtual machine between a point in time at which the virtual disk associated with the third virtual machine was created and a point in time at which the snapshot of the virtual disk associated with the third virtual machine was obtained.

17. A method for creating a backup of a first virtual machine running on a first host computer in a network of host computers, comprising: generating a second virtual machine running on a second host computer in the network of host computers, the second virtual machine being a copy of the first virtual machine; obtaining a snapshot of a virtual disk associated with the second virtual machine; creating a first backup based on at least the snapshot of the virtual disk associated with the second virtual machine; generating a third virtual machine running on a host computer in the network of host computers, the third virtual machine being a copy of the first virtual machine at a point in time after the a virtual disk associated with the first virtual machine was copied to create the virtual disk associated with the second virtual machine; obtaining a snapshot of a virtual disk associated with the third virtual machine; and creating a second backup based on at least the snapshot of the virtual disk associated with the third virtual machine.

18. The method of claim 17 , wherein creating the second backup based on at least the snapshot of the virtual disk associated with the third virtual machine comprises creating an incremental backup, wherein creating the incremental backup comprises: tracking changes to the virtual disk associated with the first virtual machine between a point in time at which the virtual disk associated with the first virtual machine was copied to create the virtual disk associated with the second virtual machine and a point in time at which the virtual disk associated with the first virtual machine was copied to create the virtual disk associated with the third virtual machine; tracking changes to the virtual disk associated with the second virtual machine; and tracking changes to the virtual disk associated with the third virtual machine.